Registration Dossier
Registration Dossier
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EC number: 235-013-2 | CAS number: 12055-23-1
Endpoint summary
Administrative data
Description of key information
Additional information
Aquatic compartment:
Three studies with aquatic invertebrates, algae and fish were carried out with HfO2 at saturated concentrations.
The first one assessed the acute toxicity to Zebrafish (Brachydanio rerio), over an exposure period of 96 hours in flow through conditions.
The second one was performed onDaphnia magna, over an exposure period of 48 hours in a semi-static system.
And the third assessed the effect of HfO2 on algal growth using the unicellular green alga Pseudokirchneriella subcapitata (Selenastrum capricornutum), over an exposure period of 72 hours.
One concentration at the solubility limit of the test item in the test medium (100 % v/v saturated solution) plus an untreated control were tested in limit tests.
In the conditions of these three tests, Hafnium dioxide had no toxic effect at aquatic water solubility limit (<0,008 mg Hf/L) on fish, invertebrate and algae; the LC50 results and the NOEC are higher than the solubility limit of the test item in the test medium.
These three tests showed no hazard to these three trophic levels due to short term exposure of HfO2.
Microorganisms/ sewage treatment plant:
The extremely low water solubility of HfO2 and its affinity to form complexes with organic molecules in water (see explanation for Kd values just above), makes it not bioavailable to aquatic organisms. Moreover, the nature of the substance (inorganic), suggests that no biological treatment is expected for this substance. But in case a WWTP with several treatment steps exists on site, Hf compounds will then be removed in the primary settling tank, due to adsorption on particulate matter and exposure of micro-organisms is unlikely.
Sediment organisms:
There is no data for sediment species, but considering the very low water solubility of HfO2, it is not expected that it is present in the pore water of sediment, where sediment-dwelling organisms can be found. In addition, no effects have been observed in pelagic organisms (daphnia and fish) in acute tests with HfO2. In conclusion, it can be reasonably assumed that HfO2 concentrations will not reach sufficiently high levels to be able to exert toxic effects to benthic organisms.
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